1. Field of the Invention
This invention relates to liquid crystal display devices, and in particular, to a method for sealing a liquid crystal inlet through which liquid crystal is injected into a liquid crystal container.
2. Description of the Prior Art
In recent years, liquid crystal displays have been increasingly used in various types of electronic equipment.
A liquid crystal display device is, for example, composed of a liquid crystal container, in which a liquid crystal is injected. The liquid crystal container comprises two transparent electrode substrates, each having a transparent electrode formed on one surface thereof, facing each other with a small distance between them, which are sealed around the circumference.
In such a liquid crystal display, the uniformity of the liquid crystal display screen is a critical factor for display performance. In a TN-Type liquid crystal display, for example, a difference in the thickness of the liquid crystal container will cause color irregularity to occur when no electric field is applied in a normally black mode, and will also cause differences in electro-optic properties to occur, resulting in unsatisfactory display quality. Therefore, the unevenness in the thickness of the liquid crystal chamber should be within .+-.0.2 microns.
Although conventional liquid crystal chambers use spherical spacers of glass or plastic between the two transparent electrode substrates facing each other to keep the thickness of the liquid crystal cell uniform, the transparent electrode substrates may be deformed during the baking of the sealant used around the circumference of the liquid crystal container, and also by the entrance of foreign matter into the container. It was difficult to obtain liquid crystal containers of a uniform thickness.
This disadvantage becomes more significant with increases in the chamber size, and particularly, the thickness of the liquid crystal container tends to be larger than the diameter of the spacers at the central portion.
To solve such a problem, a method has been adopted to assure uniform thickness of the liquid crystal container by pressurizing the liquid crystal container after injecting the liquid crystal, in the direction in which the transparent electrode substrates are stacked, under a pressure of about 150 g/cm.sup.2 for about one hour, and by sealing the liquid crystal inlet with a sealant such as an ultraviolet curing resin.
By the above described method, however, although the thickness of the liquid crystal container may be made uniform throughout, the sealant may permeate into the display area of the liquid crystal container or to the vicinity thereof in 10 to 20 seconds after sealing the liquid crystal inlet, resulting in low yields. This problem was difficult to solve even if a sealant with high viscosity is used.